From the Guidelines
Oral valacyclovir is generally well-tolerated, but it can cause side effects such as nausea or headache, as reported in a 2009 guideline by the CDC, NIH, and HIV Medicine Association 1. When taking oral valacyclovir, patients may experience:
- Nausea
- Headache
- Stomach pain
- Dizziness
- Vomiting
- Diarrhea
- Fatigue These side effects are typically mild and often resolve as the body adjusts to the medication. It is essential to note that no laboratory monitoring is needed in patients receiving episodic or suppressive therapy unless the patient has substantial renal impairment 1. However, in rare cases, valacyclovir can cause more severe side effects, such as thrombotic thrombocytopenic purpura/hemolytic uremic syndrome, which has been reported in HIV-infected patients treated with high-dose valacyclovir 1. To minimize the risk of kidney-related side effects, staying well-hydrated while taking valacyclovir is crucial. If patients experience severe or persistent side effects, they should contact their healthcare provider immediately rather than discontinuing the medication on their own.
From the FDA Drug Label
The most common adverse reactions reported in at least 1 indication by greater than 10% of adult subjects treated with VALTREX and observed more frequently with VALTREX compared with placebo are headache, nausea, and abdominal pain. The only adverse reaction reported in greater than 10% of pediatric subjects aged less than 18 years was headache In clinical trials for the treatment of cold sores, the adverse reactions reported by subjects receiving VALTREX 2 grams twice daily (n = 609) or placebo (n = 609) for 1 day, respectively, included headache (14%, 10%) and dizziness (2%, 1%). Genital Herpes Initial Episode: In a clinical trial for the treatment of initial episodes of genital herpes, the adverse reactions reported by greater than or equal to 5% of subjects receiving VALTREX 1 gram twice daily for 10 days (n = 318) or oral acyclovir 200 mg 5 times daily for 10 days (n = 318), respectively, included headache (13%, 10%) and nausea (6%, 6%) Suppressive Therapy: Suppression of Recurrent Genital Herpes in Immunocompetent Adults: In a clinical trial for the suppression of recurrent genital herpes infections, the adverse reactions reported by subjects receiving VALTREX 1 gram once daily (n = 269), VALTREX 500 mg once daily (n = 266), or placebo (n = 134), respectively, included headache (35%, 38%, 34%), nausea (11%, 11%, 8%), abdominal pain (11%, 9%, 6%)
The common side effects of oral valacyclovir include:
- Headache
- Nausea
- Abdominal pain These side effects were reported in greater than 10% of adult subjects treated with valacyclovir 2.
From the Research
Oral Valacyclovir Side Effects
- The most common side effect of oral valacyclovir is headache, as reported in studies 3, 4.
- High-dose prophylactic valacyclovir therapy (8 g/day) for CMV disease for prolonged periods may cause a potentially fatal thrombotic microangiopathy (TMA)-like syndrome, particularly in immunocompromised patients with advanced HIV disease 3.
- Gastrointestinal complaints were also reported in patients receiving high-dose valacyclovir 3.
- Oral valacyclovir is generally well tolerated at dosages used to suppress recurrent episodes of genital herpes (500 to 1000 mg/day) in immunocompetent and HIV seropositive individuals 3, 4.
Comparison with Other Antiviral Agents
- Valacyclovir has been compared to aciclovir and famciclovir in several studies, with similar efficacy and tolerability profiles 3, 4, 5, 6.
- Valacyclovir may be a safer alternative to acyclovir in patients with renal dysfunction, as acyclovir is known to be nephrotoxic 7.